This invention relates generally to data communications networks, and more particularly, to a method and apparatus for trunking of physical ports that reside on different switches within the network.
Computer networks are used to interconnect many computing resources, including computers, workstations, servers, printers, modems, and storage devices. For example, two or more computers may be connected together through a network. Network users are able to share files, printers and other resources, send messages and run applications on remote computers. An important part of any computer network includes the physical components or network communications devices used to interconnect the computing resources.
One network communications device used to interconnect multiple computing resources is a chassis-based system designed to accommodate a number of internal cards. The computing resources such as computers are coupled to the internal cards of the chassis-based system. Once the computers are coupled to the internal cards, the computers are coupled to the network. To accommodate network growth, additional internal cards may be purchased and added to the chassis-based system. With the additional internal cards installed, additional computing resources may be added to the network. A disadvantage of these chassis-based systems is that there is a relatively large initial investment when purchasing the chassis because of the large amount of overhead associated with chassis-based systems.
An alternative to expensive chassis-based systems is the use of less expensive standalone network communications devices or units that have a fixed number of ports for connecting computing resources or stations to the network. Such standalone network communications devices include stackable switches or the like. Although additional ports can not be added to each individual standalone unit, separate standalone units can be stacked, cascaded or coupled to accommodate network growth. As a result, there is a lower startup cost when establishing a computer network with the standalone units in comparison with chassis-based systems. Furthermore, network administrators still have the flexibility to increase the size of the network with the less-expensive standalone units.
FIG. 1 illustrates multiple network communications devices 103, 105, 107, 109 and 111 coupled together to form a computer network 101. Multiple computing resources (not shown) are coupled to each network communications device 103, 105, 107, 109 and 111. In one embodiment, network communications devices 103, 105, 107, 109 and 111 are stackable switches coupled together through bus 113. Bus 113 is used to tie together the switch network fabric of computer network 101. It are noted by one of ordinary skill in the art that the utilization of bus 113 is an extension of the chassis-based designs discussed earlier. The internal cards of the chassis-based systems are commonly coupled to high speed buses within the chassis-based systems.
The use of stackable switches allows network administrators to build systems having multiple physical ports to a computing resource with a high data bandwidth requirement, such as a network file server. Multiple physical ports to a single resource is known as multi-link trunking, and allows load balancing, where the network traffic to a single computing resource can be shared across the physical ports to the resource.
Known systems allow trunking to a single computing resource only if the multiple physical ports to the resource are all connected to the same network switch. However, it is common for a single computing resource to have physical ports to more than one switch. If the physical links on different switches cannot be trunked, the available bandwidth of the extra links is often wasted. In addition, unless data frames can be sent through local trunks, bandwidth is wasted because duplicate frames typically must be sent to all switches on the network. Therefore, there is a need to enable trunking of physical ports that reside on different switches within the network. There is a future need to forward data frames through local trunks.
The present invention provides a method and apparatus for providing data communication between a source station having multiple connections to a first switch and a destination station having multiple connections to a second switch. A trunk identifier to each port on the first switch and each port on the second switch. A data frame is encoded with the trunk identifier for an ingress port on the first switch. The data frame is sent to the second switch from the first switch. A list of egress ports for the destination station is obtained from a station list contained in the second switch. An egress port is selected from the list of egress ports based upon the source address, destination address and trunk identifier. The data frame is sent to the destination station through the selected egress port.